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SubjectRE: [PATCH v2 char-misc 1/1] x86/hyperv: Add interrupt handler annotations
Date
> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Wednesday, April 4, 2018 1:16 AM
> To: Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>
> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org; olaf@aepfle.de;
> apw@canonical.com; vkuznets@redhat.com; jasowang@redhat.com;
> leann.ogasawara@canonical.com; marcelo.cerri@canonical.com; Stephen Hemminger
> <sthemmin@microsoft.com>; KY Srinivasan <kys@microsoft.com>
> Subject: Re: [PATCH v2 char-misc 1/1] x86/hyperv: Add interrupt handler annotations
>
> On Tue, Apr 03, 2018 at 01:59:08PM -0700, mhkelley58@gmail.com wrote:
> > From: Michael Kelley <mikelley@microsoft.com>
> >
> > Add standard interrupt handler annotations to
> > hyperv_vector_handler().
> >
> > Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> > ---
> > Changes in v2:
> > * Fixed From: line
> > ---
> > arch/x86/kernel/cpu/mshyperv.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 4488cf0..20f6849 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -41,7 +41,7 @@ static void (*hv_stimer0_handler)(void);
> > static void (*hv_kexec_handler)(void);
> > static void (*hv_crash_handler)(struct pt_regs *regs);
> >
> > -void hyperv_vector_handler(struct pt_regs *regs)
> > +__visible void __irq_entry hyperv_vector_handler(struct pt_regs *regs)
>
> What bug does this solve? What is wrong with the existing markings?
> What does __visible and __irq_entry give us that we don't already have
> and we need?
>
> Are you really using LTO that requires this marking to prevent the code
> from being removed?

Thomas Gleixner commented on Vitaly Kuznetsov's Hyper-V reenlightenment patch
that the interrupt handler should have these annotations: see
https://lkml.org/lkml/2018/1/14/145

I put the same annotations on the interrupt handler for stimer0 Direct Mode,
So this change makes the hyperv_vector_handler() consistent with
hv_stimer0_vector_handler() in the same source file. It does not fix any
immediate bug -- it's for consistency and alignment with what is apparently
standard practice.

Not sure what LTO is ...

Michael

>
> thanks,
>
> greg k-h

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